This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A274987 #14 Nov 22 2016 21:21:54
%S A274987 3,5,7,11,13,17,23,31,37,53,59,61,73,79,83,89,101,103,109,127,137,139,
%T A274987 149,173,179,193,223,229,257,263,293,307,313,337,347,349,359,367,389,
%U A274987 397,409,419,439,449,461,467,487,491,521,547,571,577,599,601,619,631
%N A274987 Primes p such that A274601(p) is a prime.
%C A274987 It is conjectured that the sequence is infinite.
%C A274987 This sequence is also the list of primes with k trits that are used in decomposition of 2*3^k into the sum of such two primes. k>=1.
%H A274987 Lei Zhou, <a href="/A274987/b274987.txt">Table of n, a(n) for n = 1..10000</a>
%e A274987 For p=2, A274601(p) = 4, which is not a prime, so ignore 2.
%e A274987 For p=3, A274601(p) = 3, which is a prime, so a(1)=3.
%e A274987 For p=5, A274601(p) = 13, which is a prime, so a(2)=5.
%t A274987 p = 2; Table[While[p = NextPrime[p]; cp = 2*3^(Floor[Log[3, 2*p - 1]]) - p; !PrimeQ[cp]]; p, {n, 1, 56}]
%Y A274987 Cf. A134021, A274601, A002375.
%K A274987 nonn,base,easy
%O A274987 1,1
%A A274987 _Lei Zhou_, Nov 11 2016